1. Technical Field
The present invention relates to an optical filter device and a manufacturing method for the optical filter device.
2. Related Art
An interference filter in which reflective films are arranged to be opposed to each other across a predetermined gap on opposed surfaces of a pair of substrates is known. An optical filter device in which such an interference filter is housed in a housing (see, for example, JP-A-2008-70163 and JP-T-2005-510756) is also known.
An infrared gas detector (an optical filter device) described in JP-A-2008-70163 includes a package (a housing) including a tabular pedestal (base substrate) and a cylindrical cap. In the housing, a peripheral edge portion of the base substrate and a cylindrical end portion of the cap are connected by welding or bonding. A space for housing a Fabry-Perot filter (an interference filter) is provided between the base substrate and the gap. In the optical filter device, the interference filter is bonded and fixed to a detecting unit and the detecting unit is bonded and fixed on a pedestal of a can-shaped package.
JP-T-2005-510756 describes an optical filter device (a photoelectronic device) in which a tunable optical filter (an interference filter) is fixed and housed on the inside of a package (a housing). In the optical filter device, the interference filter is arranged in a vertical stack attached to the upper surface of a header (a base substrate) of the housing.
As explained above, JP-A-2008-70163 and JP-T-2005-510756 describe that the interference filter is housed and fixed on the inside of the housing but do not describe a specific method therefor.
For example, it is likely that the reflective film warps due to a difference between the coefficients of thermal expansion of the interference filter and the base substrate to which the interference filter is fixed. When the interference filter and the base substrate are fixed by an adhesive, it is likely that the reflective film warps due to contraction of the adhesive when the adhesive hardens. When the reflective film of the interference filter warps, the optical characteristics of the interference filter is affected.